The present invention relates to systems for disposing of sludge material. In particular, the present invention relates to a sludge material handling system in which a positive displacement pump, a sludge material feed system which delivers sludge to the positive displacement pump and a sludge material disposal system which receives and disposes of sludge from the positive displacement pump can be controlled as a function of an actual volume of sludge delivered by the pump during one or more pumping cycles.
In recent years, sludge pumps have found increasing use for conveying sludge through pipelines in municipal and industrial applications. Positive displacement sludge pumps offer a number of significant advantages over screw or belt conveyers. For example, a positive displacement sludge pump can pump sludge through a pipeline while containing odors in order to maintain a safe and secure working environment. Positive displacement pumps are capable of pumping thick, heavy sludge materials which may not be practical for belt or screw conveyers. This is particularly important where the sludge material needs to be dried and burned in an incinerator.
Pump and pipeline systems also take up less space than screw or belt conveyers and, with the use of simple elbow pipes, are capable of transporting sludge materials around corners. Additionally, positive displacement sludge pumps offer a reduction in noise over mechanical conveyers as well as greater cleanliness and reduced spillage.
Various state and federal regulations covering the processing and disposal of sludge require that the processor accurately measure and record the amount of material handled. Positive displacement sludge pumps such as those described in Oakley et al., U.S. Pat. No. 5,106,272, entitled "SLUDGE FLOW MEASURING SYSTEM", can accurately measure the volume of sludge transported. Oakley et al., discloses a system for transporting high solids sludge which includes a positive displacement pump for pumping sludge through a pipeline. The volume of sludge transported is accurately measured by determining the fill percentage of the pumping cylinder during each pumping cycle. The fill percentage is determined by using any of a number of sensed parameters including material flow signals, measured time intervals, hydraulic fluid pressure, and hydraulic fluid flow rate during each pumping cycle.
One embodiment of the system and pump disclosed in Oakley et al., includes a valve, commonly referred to as a poppet valve, between the pumping cylinder and the outlet which opens and connects the pumping cylinder to the outlet only when the pressure within the pumping cylinder essentially equals the pressure at the outlet. The timing of the opening of the outlet poppet valve during the outlet stroke provides a means for determining the fill percentage or the total volume delivered during each pumping stroke.
A second embodiment of the system and pump disclosed in Oakley et al. includes and outlet valve, commonly referred to as a pivoting transfer tube valve, which connects the outlet to the pumping cylinder during the entire pumping stroke. In this embodiment, both the hydraulic pressure driving the piston and the outlet pressure are sensed during the pumping stroke. Determining either the time or the piston position during each pumping stroke when the hydraulic pressure equals the outlet pressure can be used to derive a fill percentage or volume delivered during each of the pumping strokes.
In a typical sludge material handling system, a sludge material feed system delivers sludge to the positive displacement pump. The sludge material feed system may include a belt press, an auger, a centrifuge or other devices for drying the sludge and/or delivering it to the positive displacement pump.
The sludge material handling system also typically includes a sludge material disposal system which disposes of sludge pumped by the positive displacement pump. Typically, the sludge material disposal system will include an incinerator which incinerates the sludge. However, the sludge material disposal system could include other means of disposing of the sludge material in accordance with Environmental Protection Agency (EPA) regulations. For example, the sludge material disposal system could include a truck which transports the sludge to a remote area where it is spread out over the ground.
In any case, EPA regulations frequently require accurate measurement and recording of the amount of sludge which is being disposed. In most instances, a sludge material handling system requires at least three or four individuals to monitor and control the sludge material feed system, the positive displacement pump and the sludge material disposal system. Employing a number of individuals to monitor and control the sludge material handling system adds significant cost to the disposal of sludge. Additionally, present systems leave room for human error and makes it difficult to keep accurate records of the amount of sludge handled by the system. Keeping accurate records is typically necessary to satisfy EPA requirements.